[1.x] Adds --dirty option

[nunomaduro]

This pull request, developed in collaboration with @jasonmccreary, adds the --dirty option to Pint. When this option is used, Pint will only apply styling changes to added or edited files in a Git repository.

This means that when you use this option in a pull request for your project, Pint will style only the files you have added or edited, and not style any files that were not modified by your pull request.

pint --dirty

[jasonmccreary]

@nunomaduro, thanks for the guidance. I'll get this patched up in the next live stream unless baby Emma comes early. 👨‍🍼

[jasonmccreary]

Just finished up my live stream. I got items 1 and 2 working. A quick caveat though, the --path option does not exist. So item 1 works by using the first path passed (or the default of the current working directory).

In reviewing that and item 3, it appears pint does not currently honor the configuration file within the passed path when run from another directory (e.g. pint /workspace/laravelshift.com). This needs to be tested and/or patched before this --dirty option can be added with the desired behavior.

[dillingham]

Looks cool!, Currently using lint-staged for this

"lint-staged":{
        "**/*.{php}": [
            "./vendor/bin/pint"
        ],
        "resources/js/**/*.{js,vue}": [
            "prettier --write",
            "eslint --fix"
        ]
    }